The present invention relates generally to store carriers for carrying a releasable store on an aircraft and, more particularly, to an improved ejection system capable of maximizing the pneumatic force available for ejecting the store while reducing the overall complexity of the ejection system, resulting in enhanced in reliability of operation.
Military aircraft utilize racks located beneath the wings and fuselage to carry and dispense stores upon command. Stores may be used to contain munitions i.e. bombs, or to contain other material to be dropped from the aircraft i.e. rockets or missiles upon command. Typical ejector racks are shown in U.S. Pat. Nos. 4,043,525 and 4,347,777, each issued to the same inventor and assignee of the present invention and incorporated herein by reference.
Conventionally, an ejector rack includes a release mechanism which is activated to mechanically release and subsequently forcibly eject the weapon from the aircraft. Most ejector racks at one time utilized pyrotechnic (explosive) cartridges which, upon ignition, generate high pressure gas for actuating the mechanical release mechanism, as well as providing high pressure gas to forcibly eject the store from the rack mounted on the aircraft.
Ejection systems that employ pyrotechnic cartridges have certain undesirable characteristics. For example, a great deal of cleaning and maintenance is required after firing a pyrotechnic cartridge. When fired, the chemical burning of the explosive charge within the pyrotechnic cartridge results in a large amount of residue being deposited within the system. This residue also contains moisture and corrosives. After burning, the moisture in the system tends to further gather debris, form ice, and otherwise clog the internal and external workings of the bomb rack mechanism. If not properly disassembled and cleaned after a scheduled number of firings, at high cost and a great deal of labor and downtime for the aircraft, an ejection system utilizing pyrotechnic cartridges will quickly corrode and become unreliable.
In order to avoid the inherent problems associated with the pyrotechnic cartridge, the inventor of the present invention devised a unique pneumatic ejector rack assembly set forth in U.S. Pat. No. 5,583,312 (hereinafter referred to as the '312 patent) entitled COLD GAS EJECTOR RACK, issued Dec. 10, 1996, assigned to the assignee of the present application and incorporated herein by reference. The '312 patent describes a pressurization system capable of servicing one or more store release systems, which system uses air or one of any number of clean, non-pyrotechnic pressurized gases both as the energy source and energy transfer medium. Preferably, the aircraft contains a miniature compressor and purification system. Ambient air is filtered, dried and stored as an energy medium. Using purified air eliminates the excessive cleaning burden imposed when using pyrotechnics, and also eliminates the sealing problems associated with hydraulics.
As described in detail in the '312 patent, the ejection system includes an on-board source of pressurized non-pyrotechnic gas, at least one release mechanism for mounting the store on the aircraft, and an actuation system for driving the release mechanism between closed and open positions. The actuation system includes an accumulator for receiving and storing pressurized gas from a source which may or may not be located on-board the aircraft. Actuation of a control valve causes a primary valve to move in a linear direction from a closed position to an open position (see FIG. 3 of the '312 patent). This movement allows pressurized gas, i.e. air, to flow from the accumulator into the actuation chamber, forcing a separate, hook release piston to move in a linear direction as shown in the same FIG. 3 of the '312 patent. As a result, the pressurized gas forces a ram attached to the hook release piston to engage and unlock the hooks holding the stores to the rack. Pressurized gas entering the actuator chamber is further capable of exiting from an opposite end of the actuator chamber and flowing into one or more feed tubes that deliver the pressurized gas into engagement with thrust pistons, wherein the pressurized gas causes the thrust pistons to forcibly eject the newly unlocked stores from the rack.
While the ejection system disclosed in the '312 patent provides a significant improvement over earlier pyrotechnic ejection systems due to a substantial reduction in the amount of required maintenance that needs to be performed as compared to the maintenance performed on a pyrotechnic driven ejection system, it has been discovered that by employing a pneumatically powered primary valve reciprocating along a first axis and a separate release piston reciprocating along a second, non-aligned axis as disclosed in the '312 patent, there is a significant reduction in the usable volume of the accumulator. This reduction in volume occurs due to the fact that the primary valve extends into a portion of the volume that would otherwise be available to the accumulator. In order for the accumulator to accommodate enough pressurized gas to provide sufficient force to unlock the hooks and forcibly eject the stores, the volume of the accumulator needs to be increased. This is achieved by increasing the outer surface area of the accumulator, as shown by the shape of accumulator 22 surrounding the actuator assembly in FIG. 2 of the '312 patent, making it difficult for the pneumatic ejection system described in the '312 patent to occupy the same breech volume as occupied by a conventional pyrotechnic cartridge ejection system. In effect, the ejection system disclosed in the '312 patent is able to reduce the overall maintenance requirements of the actuator assembly at the unsatisfactory cost of an increase in size of the accumulator. As a result, the ejection system may not fit in a rack previously designed to employ a pyrotechnic cartridge without significant redesign.
Based on the above and foregoing, it can be appreciated that there presently exists a need in the art for an ejection system actuator mechanism that utilizes pneumatic pressure to forcibly eject stores from their respective racks while still fitting within a conventional breech volume initially designed for pyrotechnic cartridges. The successful solution should maximize the pneumatic pressure while, at the same time, minimizing both the volume and complexity of the actuator mechanism. The present invention provides a successful solution and thereby fulfills this need in the art.